He wrote the lyrics for the stage adaptation of Disney's The Little Mermaid (2008), replacing the animated film's original lyricist Howard Ashman, who died in 1991.[3] He is working with Menken on the new musical version of Leap of Faith.[4]

Slater and his wife, Wendy Leigh Wilf, wrote the book, music and lyrics to a new musical Beatsville that received a production at the 2008 NAMT Festival of New Musicals, in New York.[5]

He has also composed the lyrics and co-wrote the book for the major Andrew Lloyd Webber musical Love Never Dies, which is a sequel to Lloyd Webber's 1986 musical The Phantom of the Opera. The show premiered in the West End in March 2010.[6] After widespread criticism of Slater's lyrics on the show's opening, Charles Hart was brought in to substantially rewrite parts of the libretto.